SLI new build for WoW?

I'm building a new computer.

i7-930 cpu (2.84 ghz I believe?)
2 - 640 gb HDD in raid 0
6gb ddr3 ram 1600
win 7

I run dual monitors 23" @ 1920 x 1080

**500w OCZ PSU** EDIT: Will I need more PSU?

I have a 8800gt 512 mg 256 bit VC, on a duo core 6400rpm 2.13 ghz Velocity micro, running Vista OS with a lot of resource hoggers turned off.

I was thrilled with the VC when I bought it.

I am seeing lower fps nowadays.

My options are:

1. Use my old 8800gt in the new comp. But I was thinking of using that comp as a backup. However, I can use it and get new VC's later as well.

2. Buy 1 VC that MUST perform better than the 8800gt noticeably, but within a budget of say under $200 and prefer lower the better. ** I have no idea what VC that would be and am open to suggestions.

3. Find a 8800 gt somewhere (mine is BFG will it matter?), pull out the old one and go SLI on the new system.

4. Buy 2 VC's for SLI or Crossfire, but that I'm sure is the most expensive route and I dont really want to get into the $300 + route if possible.

If I could go SLI/Crossfire for a reasonable budget amount would the performance for WoW be greatly increased (I run higher settings 1920x1080 with a buttload of addons)


Thanks for your advice.